IGBTs are power semiconductor components which are used, for example, as switches in high power applications. An IGBT is a gate controlled component, which can be turned on and off from its gate.
The properties of IGBTs can make them very attractive to be used in high-power applications, since IGBT switches are able to switch high currents at high voltage levels. Further, IGBT switches are fast in operation, with tolerable turn-on and turn-off losses. This is due to the fact that simultaneous time of the voltage over the component and current through the component is short.
IGBTs can include a gate drive circuit which is able to quickly charge the internal capacitances of the component for turning on the component. Similarly, the drive circuit can remove the charge from the gate for cutting the current from the component. The gate drivers are connected to the gate and emitter terminals of the components, and a purpose of the driver is to control the potential of the gate with respect to the emitter. When an IGBT is turned on, the gate is made positive with respect to the emitter, and when a turn-off is desired, the potential of the gate is made negative with respect to the emitter.
For this purpose, gate driver circuits include a two-sided auxiliary voltage, from which positive and negative gate voltages with respect to an emitter can be derived. This two-sided voltage can be generated from a voltage divided with a series connection of capacitors such that a midpoint of the capacitors can be connected to the emitter of the controlled component. Either a positive or negative voltage with respect to the emitter can then be controlled at the gate.
Gate driver circuits can also shut down the controlled IGBT in the event of excessive current flowing through the component. Over current situations, which can be generated by short circuits, should be removed from the circuit by shutting down the component in question. The IGBT which is conducting an over current cannot be turned off in a normal manner, since the quick removal of excessive current would cause voltage spikes across the collector and emitter of the component. This voltage spike could destroy the component and the devices connected to the component.
Known gate driver circuits which are also operable to remove short circuit current using soft shutdown can be complicated structures having many different components and therefore involving a large surface area. An example of a gate driver circuit is presented in U.S. Pat. No. 6,335,608.